The present invention relates to an ion exchanger.
When a fuel cell is installed in a vehicle, a cooling circuit, through which coolant flows to cool the fuel cell, is provided for the purpose of limiting the temperature increase of the fuel cell upon generation of electric power. However, when coolant cools the fuel cell, constituents of the coolant are decomposed by heating to produce ions, which increases the ions in the coolant. The ions may cause corrosion of metal or a decline in the function of the fuel cell. Thus, the cooling circuit is provided with an ion exchanger that removes ions from the coolant by adsorbing ions contained in the coolant.
Such ion exchangers are disclosed in, for example, Japanese Laid-Open Patent Publication No. 2011-83744, Japanese Laid-Open Patent Publication No. 2013-233499, and Japanese Patent No. 4113715. The ion exchangers each include a case, which is provided with an opening, an intake port, and a discharge port, an ion exchanging resin member, which is arranged in the case, and a cap, which is detachably attached to the opening of the case. Coolant is drawn in through the intake port and discharged through the discharge port. The ion exchanging resin member removes ions from the coolant. The cap closes the opening of the case. The coolant flowing through the cooling circuit flows into the case of the ion exchanger through the intake port. Ions are removed when the coolant travels through the ion exchanging resin member in the case. Ions are removed from coolant in this way, and the coolant flows out of the case (the cooling circuit) through the discharge port.
In the above-described ion exchangers, the ion exchanging resin members remove ions contained in coolant by adsorbing them. Thus, it is necessary to periodically replace the ion exchanging resin members. In the ion exchanger disclosed in Japanese Laid-Open Patent Publication No. 2011-83744, the opening of the case is formed to open downward at the lower end of the case. Thus, it is necessary to attach or detach the cap that closes the opening at the lower end of the case. In addition, it is necessary to replace the ion exchanging resin member in the case through the opening that is located at the lower end of the case. This decreases the workability when the ion exchanging resin member is replaced.
In the ion exchanger disclosed in Japanese Laid-Open Patent Publication No. 2013-233499, the opening of the case is formed to open upward at the upper end of the case. This configuration avoids decrease of workability unlike the previous case, in which the cap needs to be attached or detached at the lower end of the case, and the ion exchanging resin member in the case needs to be replaced through the opening located at the lower end of the case. However, the ion exchanger of publication No. 2013-233499 has the following problem. That is, the intake port through which coolant is drawn in is formed in the upper end portion of the case, and a pipe through which the coolant in the cooling circuit is drawn in is connected to the intake port. Thus, when the cap and the ion exchanging resin member are attached to or detached from the case, the pipe coupled to the intake port becomes an obstacle. This disturbs the work for replacing the ion exchanging resin member.
As known from the above matters, it is preferable for the opening, the intake port, and the discharge port to be arranged in the case in the following manner to limit decrease of workability in replacing the ion exchanging resin member. That is, as in the ion exchanger disclosed in Japanese Patent No. 4113715, the opening of the case is formed to open upward at the upper end of the case, and the intake port, through which coolant is drawn into the case, and the discharge port, through which coolant is discharged out of the case, are arranged in the lower portion of the case. This configuration allows the cap, which closes the opening of the case, to be attached or detached at the upper end of the case, and allows the ion exchanging resin member in the case to be replaced through the opening that is located at the upper end of the case. Furthermore, since the intake port and the discharge port are arranged in the lower portion of the case, when the cap and the ion exchanging resin member are attached to or detached from the case, pipes coupled to the intake port and the discharge port do not become obstacles.
Use of the ion exchanger of Japanese Patent No. 4113715 limits decrease of workability in replacing the ion exchanging resin member. However, it is difficult to discharge the air that enters the case during the replacement out of the case through the discharge port.
This is because air in the case accumulates on the inner top surface in the upper end portion of the cap by buoyancy when the coolant flows in the case, and at the same time, the coolant that travels through the ion exchanger is drawn into the case through the intake port, which is arranged in the lower portion of the case, and travels through the ion exchanging resin member, and, after that, the coolant flows out of the case through the discharge port, which is arranged in the lower portion of the case like the intake port.
Depending on the above-described flow of the coolant in the case, air that accumulates on the inner top surface in the upper end portion of the cap cannot be pushed to the discharger port. Thus, the air stays on the inner top surface in the upper end portion of the cap. Accumulation of air on the inner top surface in the upper end portion of the cap makes it difficult to adjust the flow rate of coolant traveling through the interior of the ion exchanger (in the case) at an appropriate value. This may cause adverse influence on removal of ions from coolant by the ion exchanger.